1) On the auto setup. The SUB needs to have an 80Hz cuttoff or the calibration fails. You can turn it up after you calibrate. I think this message about fronts being small should really say that the sub seems to be a full range speaker. Wrong message assigned to the error check.

2) Ground loops. I have dealt with this extensively as I have tons of wires going all over my house. The secret to thinking this through is that you get to pick one point as ground, not two. In my case that is the power plug at the projector.

I ran some romex down to the audio equipment from the same circuit as the projector. I was getting audio and video hum. The video hum was faint rolling bars that go down the screen slowly.

Next, I ran a wire from that ground point to ground all the antenna leads that come into the house. Both the off the air and the satellite are grounded to this same reference. Use these RF ground blocks and run a wire to the point you are calling fround.

Next, anything that goes off to another room and will by necessity be grounded there gets its ground broken and a little ground isolator composed of a couple of capacitors (one in the center conductor and one in the ground). This includes RF and SPD/IF connections.

Before I did this, the antenna lead to my daughters room would cause hum.

You can disconect leads one at a time but you may not have to isolate as many leads if you pick your ground reference correctly.